Rotary kiln and method of burning material therein



Jan. 22, 1963 1-. H. DANE ETAL 3,074,705

ROTARY KILN AND METHOD OF BURNING MATERIAL'THEREIN Filed Aug. 17, 1961 V1); kM ZM Wm! K747 L 4. W1 7;

United States PatentOfilice 3,074,705 Patented Jan. 22, 1963 3,074,705 ROTARY KILN AND MEZTHUD F BURNENG MATERIAL THEREHN Tags Halfdan Dan and Henning Ernst 0stvand Pedersen, Copenhagen-Valley, Denmark, assignors to F. L. Smidth & Co., New York, N.Y., a corporation of Delaware File-d Aug. 17, 1961, Ser. No. 132,194 Ciaims priority, application Great Britain Sept. 27, 1960 3 Claims. (Cl. 263-33) white cement and the use of the method and apparatus for that purpose will, accordingly, be described for purposes of explanation.

in the manufacture of white cement, a suitable raw material mix is burned in a rotary kiln and steps are taken to prevent the coloring of the resultant clinker by such small amounts of iron, manganese, and chromium as are frequently present in the material. For this purpose, the hot clinker leaving the burning zone is subjected to a reducing action and the reduced product is then cooled before it leaves the kiln. In the production of white cement as disclosed in the patent to Nielsen 2,015,866, issued October 1, 1935, the reducing agent is coal dust blown into the kiln through a pipe and the cooling agent is water discharged through a pipe upon the clinker close to the outlet end of the kiln.

The present invention is directed to the provision of a method of subjecting a raw material burned in a rotary kiln to successive reducing and cooling actions, which is more efiicient than the methods previously used and can be carried on more conveniently and under better control. In the practice of the method, the reducing and cooling agents are discharged upon the traveling stream of clinker in the form of sprays, which cover areas of the stream lying close together but without substantial overlap. The sprays are direccd by nozzles, which are carried by pipes adjustably mounted so that the nozzles may be easily disposed to provide the desired distribution of the agents on the surface of the clinker. At the place where the treatments occur, the surface of the clinker is inclined to the horizontal and the nozzles may be placed to discharge the sprays substantially normal to the inclined surface and thus obtain uniform distribution of the agents over the areas on which they are discharged.

For a better understanding of the invention, reference may be made to the accompanying drawing, in which FIG. 1 is a vertical longitudinal sectional view of the discharge end of a kiln for practicing the method of the invention;

FIG. 2 is a view, partly in longitudinal elevation and partly in section, of one form of the new apparatus;

FIG. 3 is an end view of the apparatus of FIG. 2;

FIG. 4 is a fragmentary transverse sectional view on the line 4-4 of FIG. 1; and

FIG. 5 is a sectional view on the line 55 of FIG. 4.

The kiln shown in PEG. 1 is of conventional construction and includes a shell it) with a lining 11 formed with an internal dam ring 12. The kiln is mounted for rotation on its axis in the usual manner and its lower end projects into a hood 13. A burner pipe 14 extends through the hood to terminate with in the kiln in the vicinity of the dam ring and conducts the primary fuel-air mixture, which is burned in the kiln. The material burned to the form of clinker C collects behind the dam ring and then overflows to issue from the lower end of the kiln into the hood. In its travel through the kiln, the material has the form of a stream, the upper surface of which is inclined to the horizontal, as indicated at S.

In the maufacture of white cement, small amounts of iron, manganese, and chromium are likely to be'present in the raw materials and the coloring action of these ingredients of the mix can be prevented by subjecting the hot clinker to a reducing operation followed by a cooling operation. For this purpose,'the kiln is provided with an inner pipe 15 andan outer pipe 16 in telescoped relation, the pipes extending through a wall 13a of the hood andinto the lower end of the kiln. The pipes are supported in a sleeve 17 attached to the outside of the wall 13a and may be slid axially and turned angularly in the sleeve and relatively to each other.

The pipe 15 is provided with a handle 18 outside the kiln, by which the pipe can be moved axially and angularly, and its outer end is connected to a hose 19, by which the pipe is supplied with a reducing agent. Inwardly beyond the inner end of pipe 16, the pipe 15 is bent at a right angle and it is provided at its end with a nozzle 20, by which the reducing agent may be discharged in the form of a solid conical spray. The section of pipe 15 within the pipe 1-6 is enclosed by a covering 21 of heat insulating material, which may be a ceramic.

The ends 16a of the pipe 16 are turned inward and closed about the insulating covering by appropriate seals. Outside the hood, the pipe 16 carries a handle 22, by which it may be slid axially on the pipe 15 and also turned angularly. An inlet fitting connection 23 leads to the interior of pipe 16 outside the hood and a hose 24 for supplying a cooling agent is connected to the fitting. Adjacent to its inner end, the pipe 16 is provided with an outlet fitting 25 on the end of which is mounted a nozzle 26 for discharging the cooling agent in the form of a solid conical spray.

extend parallel and terminate in nozzles 26 for discharg-.

ing conical sprays.

in the operation of the kiln equipped with the apparatus shown in FIGS. 1 and 4, the red hot clinker C overflowing the darn ring 12 forms a stream having the inclined surface S and the inner pipe 15 is adjusted so that it discharges a conical spray upon the clinker close to the dam ring, with the axis of the cone normal to the surface S. The spray thus covers the circular area R on the surface S and a substantially uniform distribution of the reducing agent over the area R is obtained. The outer pipe 16 is adjusted so that the axes of the conical sprays issuing from its nozzles 26' are also normal to the surfaces S and these sprays cover circular areas W on the surface S with the areas lying close to but without substantial overlap with the area R. The areas W may overlap each other is desired.

With the arrangement described, the hot clinker is subjected to a reducing operation shortly after it leaves the hot zone of the kiln and it is then immediately cooled. The reduction of the clinker followed by the rapid cooling is effective to avoid discoloration of white cement, provided the reduction takes place while the clinker is in a temperature range of approximately 50 C. which lies between 900 C. and 1300' C. and depends to some extent on the nature and amount of the constituents in the clinker which produce the discoloration. With the apparatus described, the pipe 15 may be adjusted as required by the particular materials being burnt to insure that reduction will be carried out in the best temperature interval for obtaining the maximum degree of whiteness in the product. The cooling should then begin immediately after the reduction is complete and the pipe 16 may be adjusted relative to the pipe 15 to produce the desired effect.

When a pipe 15 with a single nozzle 20* is employed, the cooling medium is discharged upon the clinker over a circular area W of approximately the same diameter as the area R. The areas R and W should then lie close together without substantial overlap. Since the pipes 15 and 16 are adjustable both axially and angularly relative to each other, it is easy to adjust them to obtain the best conditions of operation.

When a-pipe 15 having branches 27, 28 terminating in nozzles 26' is used, it is possible to discharge the reducing and cooling agents upon the clinker with less gaps between the areas covered by the agents than occurs when a single cooling agent nozzle is employed. Also, it is advantageous to use two nozzles for the cooling agent, since more of this agent is employed than of the reducing agent.

The reducing agent used in the production of white cement may most conveniently be oil carried into the kiln by means of a gaseous medium, such as air or steam under pressure, the medium serving to atomize the oil as it emerges from the nozzle. The cooling agent may be water as is customary. With the pipe 15 for the reducing agent placed inside the pipe 16 for the water, the oilsaturated mixture in the pipe 16 is protected against excessive heat in the kiln before it is discharged from the nozzle 20. The layer-of insulation 21 enclosing the pipe 15 for the reducing agent is desirable to prevent the steam used to atomize the reducing agent from condensing onthe wall of'pipe 15. The .pipe 16 may also be provided with insulation to reduce the absorption of heat from the interior of the kiln by the cooling water.

In the apparatus described, thepipe 15 for the reducing agent is bent downward in its inner end and provided with a single nozzle. However, if desired, this pipe may bB-Pl'OVidfid with lateralbranches terminating in nozzles 40 1. A method of treating burned material traveling through a rotary kiln from the burning zone in a stream having an upper surface inclined to the horizontal, which comprises reducing the burned material by directing a conical spray of a reducing agent upon an area of the inclined surface of the moving burned material with the axis of the spray normal to the inclined surface, and cooling the reduced material by directing at least one conical spray of a cooling agent upon a closely adjacent area of the inclined surface of the material with the axis of the spray normal to the inclined surface, spacing the sprays sufiiciently from each other that while said areas lie close to each other they do not substantially overlap.

2. The method of claim 1, in which the material burned is a raw material mix suitable for the production of white cement.

3. In a rotary kiln, through which material passes in a stream having an upper surface inclined to the horizontal, the combination of a pair of concentric pipes extending into the kiln through its discharge end, means for supplying a reducing agent to the inner pipe and a cooling agent to the outerpipe, means for independently supporting the pipes for adjustment angularly on their axes and lengthwise of the kiln with respect to one another, and nozzles on the pipes for discharging the contents of the respective pipes as conical sprays upon areas of the surface of the material lying close together but without substantial overlap, the axes of the nozzles being normal to the inclined surface of the material.

References Cited in the file of this patent UNITED STATES PATENTS 691,337 Carpenter Jan. 14, 1902 1,470,887 Sieck Oct. 16, 1923 2,015,866 Nielsen Oct. 1, 1935 2,118,973 Hansgirg May 31, 1938 2,584,808 Newhouse Feb. 5, 1952 2,642,273 Dube June 16, 1953 2,654,592 Harris Oct. 6, 1953 

1. A METHOD OF TREATING BURNED MATERIAL TRAVELING THROUGH A ROTARY KILN FROM THE BURNING ZONE IN A STREAM HAVING AN UPPER SURFACE INCLINED TO THE HORIZONTAL, WHICH COMPRISES REDUCING THE BURNED MATERIAL BY DIRECTING A CONICAL SPRAY OF A REDUCING AGENT UPON AN AREA OF THE INCLINED SURFACE OF THE MOVING BURNED MATERIAL WITH THE AXIS OF THE SPRAY NORMAL TO THE INCLINED SURFACE, AND COOLING THE REDUCED MATERIAL BY DIRECTING AT LEAST ONE CONICAL SPRAY OF A COOLING AGENT UPON A CLOSELY ADJACENT AREA OF THE INCLINED SURFACE OF THE MATERIAL WITH THE AXIS OF THE SPRAY NORMAL TO THE INCLINED SURFACE, SPACING THE SPRAYS SUFFICIENTLY FROM EACH OTHER THAT WHILE SAID AREAS LIE CLOSE TO EACH OTHER THEY DO NOT SUBSTANTIALLY OVERLAP. 